Anisotropy-Guided Enantiomeric Enhancement in Alanine Using Far-UV Circularly Polarized Light

Area of Science:

• Astrobiology
• Chemical Physics
• Origin of Life Studies

Background:

• Life on Earth exhibits homochirality, with genetic material and proteins made of single-handed (chiral) monomers.
• The origin of this molecular asymmetry is a fundamental question in the study of life's beginnings.
• Interstellar environments, including comets and star-forming regions, may hold clues, with evidence like chiral amino acids in meteorites and circularly polarized light.

Purpose of the Study:

• To investigate the asymmetric interaction between circularly polarized light and amino acids under simulated interstellar conditions.
• To experimentally determine if circularly polarized light can induce chiral symmetry breaking in amino acids.
• To correlate experimental findings with theoretical predictions for understanding extraterrestrial chiral asymmetry.

Main Methods:

• Amorphous films of racemic (carbon-13 labeled) alanine were exposed to far-ultraviolet circularly polarized synchrotron radiation.
• Optical purity was measured to quantify the extent of chiral symmetry breaking.
• Time-dependent density functional theory was employed to calculate anisotropy spectra and predict stereocontrol.

Main Results:

• Optical purities of up to 4% were achieved in alanine films.
• The degree of chiral symmetry breaking was found to be dependent on both the helicity and wavelength of the incident circularly polarized light.
• Experimental anisotropy spectra showed good agreement with theoretically calculated spectra.

Conclusions:

• Circularly polarized light can effectively induce chiral symmetry breaking in amino acids, supporting extraterrestrial origins for life's homochirality.
• The findings provide a framework for interpreting data from missions like the European Space Agency's Rosetta, which studied comet 67P/Churyumov-Gerasimenko.
• This research offers insights into the physical and chemical processes that may have led to the emergence of homochiral life on Earth.